1. Field of the Invention
The present invention relates to a seal structure in a scroll type compressor.
2. Description of the Related Art
In order to improve the quality of a seal in a hermetic space formed between a fixed scroll and a movable scroll, a structure in which a back pressure is applied against a rear face of a movable scroll base, as disclosed in Japanese Unexamined Patent Publication (Kokai) No. 3-92502 and Japanese Unexamined Patent Publication (Kokai) No. 11-6487, is employed. At the rear face side of the movable scroll base, a back pressure chamber is formed, into which pressure as high as the discharge pressure is introduced. The rear side of the movable scroll base is used exclusively for a suction pressure area of low pressure, and a seal ring is interposed between the back pressure chamber and the suction pressure area in order to prevent pressure leakage from the back pressure chamber to the suction pressure area. A seal ring in the compressor which has been disclosed in Japanese Unexamined Patent Publication (Kokai) No. 3-92502, is installed so as to be contiguous with the end face of a boss cylinder and the bridge structure of the movable scroll. A seal ring in the compressor which has been disclosed in Japanese Unexamined Patent Publication (Kokai) No. 11-6487, is installed so as to be contiguous with the rear face of the movable scroll base and the inner surface of the housing.
In order to prevent pressure leakage between the movable scroll wall and the fixed scroll wall, it is advisable to press the movable scroll wall against the fixed scroll wall. For this reason, a structure is known in which the movable scroll is designed so as to be able to slightly move with the eccentric shaft in the direction of radius, and the movable scroll wall is pressed against the fixed scroll wall by utilizing the pressure in the hermetic space. In such structure, the movable scroll is allowed to tilt, that is, the eccentric axis of the movable scroll is allowed to tilt with respect to the axis of the eccentric shaft in the direction of the above-mentioned movement. When the eccentric axis of the movable scroll tilts with respect to the axis of the drive shaft of the compressor, the contact between the seal ring and the counterpart thereof becomes poor. Such a poor contact allows pressure leakage from the back pressure chamber to the low pressure area, and it is impossible to maintain a desired back pressure in the back pressure chamber. If it is impossible to keep the desired back pressure in the back pressure chamber, it is difficult to maintain a high quality seal in the hermetic space formed between the fixed scroll and the movable scroll.
The objective of the present invention is to prevent the pressure leakage from the back pressure chamber installed at the rear side of the movable scroll to the low pressure area.
In the present invention, therefore, a scroll type compressor is employed, wherein: a fixed scroll, on the base of which a fixed scroll wall is formed, is opposed to a movable scroll, on the base of which a movable scroll wall is formed; a hermetic space is formed between the movable scroll wall of the movable scroll and the fixed scroll wall, and the volume of the hermetic space decreases according to the orbital movement of the movable scroll; and the rotational force of the drive shaft is transmitted to the orbital movement mechanism, which comprises an eccentric shaft to provide the orbital movement to the movable scroll so that the movable scroll is allowed to orbit. In the first aspect of the present invention, the eccentric axis of the eccentric rotation body that eccentrically rotates together with the eccentric shaft is designed to be able to move corresponding to the eccentric axis of the movable scroll, a seal member is interposed between the movable scroll and the eccentric rotation body so that the seal member circumscribes the eccentric axis of the eccentric shaft, and the back pressure chamber is formed by the movable scroll, the eccentric rotation body and the seal member.
The eccentric rotation body is able to similarly tilt according to the inclination of the movable scroll. Therefore, the seal member interposed between the movable scroll and the eccentric rotation body is always in good contact with the movable scroll and the eccentric rotation body.
The present invention may be more fully understood from the description of the preferred embodiments of the invention set forth below, together with the accompanying drawings.